1. Field of the Invention
This invention relates to a method and system for of sub-channelizing a broadband medium and assigning predefined protocols to respective subchannels thereof. More particularly, it relates to a method and system for sharing sub-channels based on the nature of the data to be transferred in a multi-channel communication network.
2. Background of Related Art
The general trend of the prior art has been to establish high bandwidth channels for the transmission of data to improve performance. For instance, recent improvements in dial-up modems has been the migration from 28.8 Kb/s to 56 Kb/s. It is conventionally assumed that larger bandwidths provide better performance. In the case of shared channels, as the bandwidth of channels increases, so does the complexity of the channel, including the protocol used. Moreover, larger bandwidths increase the possibility that noise at a particular frequency will erode the reliability of communications.
In a shared channel environment, media access protocols involve contention or polling to gain channel access. For instance, U.S. Pat. No. 5,563,883 discloses a controller which periodically broadcasts a polling message simultaneously to a plurality of cable modems over a shared downstream communication channel. The cable modems then contend for access to a single upstream channel. If messages of more than one modem collide with one another, a binary search method implemented in a media access controller arbitrates between and isolates colliding modems. However, only one upstream channel is available for the colliding modems to communicate upstream back to the controller. Thus, all modems assigned to a particular upstream channel must not only contend for channel access to respond to the downstream broadcast poll, but any subsequent data transmission must also contend for the same single upstream channel. This leads to congestion and lower performance.
U.S. Pat. No. 4,829,297 discloses a communication method wherein the same polling technique is used in two channels. While this increases performance only because it provides two upstream paths rather than just one, it fails to segregate busy users from inactive or idle users.
U.S. Pat. No. 4,754,426 teaches the prioritized polling technique of placing a higher priority on some users, and thus polling those higher priority users more frequently. However, all upstream communications remain on a single channel. Thus, the performance of the higher priority users is increased, but at the expense of the non-high priority users.
Other patents such as U.S. Pat. No. 5,572,517 to Safadi discourage the use of a polling scheme in a shared network environment altogether.